A first known issue in playing songs, whether from a radio broadcaster or at an informal gathering, is making a transition from the end of one song to the beginning of the next. Listeners desire transitions that sound natural, while songs (and other sounds) have a wide variety of beginnings and endings, at least some of which are important to presentation of the song.
A second known issue in playing songs is that of ordering a set of songs for presentation, or alternatively, of selecting a next song for presentation when one song ends. After any particular song, listeners remain relatively uninformed about which song would be best that they should play next. One known method is for a person to prepare a song sequence, sometimes known as a “playlist”, ahead of time, exercising their human judgment about which songs should follow which. This method has the first drawback that it can be time consuming, and the second drawback that it might take substantial originality to prepare a playlist that is pleasing to listeners.